Ganymede

Ganymede (Jupiter III) is Jupiter's largest moon, which is the largest moon in the solar system, larger than Mercury and Pluto. It is one of the original four Jupiter moons found centuries ago (the Galilean Moons), the third outward from Jupiter of these four, and is the seventh outward of Jupiter's currently known moons. Its radius is 2634 km (0.4 Earth's), its mass is 1.5×10²³ kg (0.025 Earth's), with a mean density about twice that of water (about 1/3 Earth's) and subsurface oceans are suspected. Ganymede's orbital period is 7 days and it is tidally locked. Its orbit is in sync with Europa (2 orbits for each Ganymede orbit, an orbital resonance) and Io (4 orbits for each Ganymede orbit). Flyby observations of Ganymede have been made by the Pioneer, Voyager, Galileo, and Juno missions, Galileo approaching 264 km from its surface. JUICE was launched in 2023 and is currently on the way to Jupiter with plans to finish its mission orbiting Ganymede.